The present invention relates to arthroplastic reconstruction of the human joints and more particularly to implant resection arthroplasty of the wrist joint.
Frequent causes of disability of the wrist joint include aseptic necrosis and arthritis of the carpal bones. Surgical treatment of wrist joint disabilities has heretofore included intercarpal fusion, wrist fusion, local resection, proximal row carpectamy, bone grafting, radial styloidectomy, radial shortening or ulnar lengthening and soft tissue interposition arthroplasty. Fusion procedures have an adverse effect on stability, power and mobility of the wrist. Local resection procedures involving the removal of irreversibly pathological bone are complicated by migration of adjacent carpal bones into the space left by the resection and resulting instability of the wrist joint.
Various forms of metallic, acrylic and silicone implants have been developed for replacement of carpal bones. The implants essentially act as articulating spacers to maintain the relationship of adjacent carpal bones after excision of the carpal bones they replace while preserving mobility of the wrist. Examples of prior carpal bone implants may be found in Applicant's work entitled "Flexible Implant Resection Arthroplasty On The Hand And Extremities", 1973 by C.V. Mosby Company; U.S. Pat. No. 4,198,712 entitled SCAPHOID IMPLANT and issued on Apr. 22, 1980 to the Applicant; and U.S. Pat. No. 4,164,793 entitled LUNATE IMPLANT and issued on Aug. 21, 1979 to Applicant.
The prior carpal scaphoid implants have been of two basic types. The implant described in Applicant's aforementioned work is shaped essentially as an anatomical replica of the carpal scaphoid. The implant does, however, have more pronounced concavities to provide for greater stability. The implant has an intramedullary stem that fits into the trapezium bone to maintain anatomical positioning postoperatively until a firm capsuloligamentous system has healed around the implant. The implant described in aforementioned U.S. Pat. No. 4,198,712 departs from the anatomical replication of the scaphoid bone. The implant includes an inferior surface defining a trapezium articulate facet and a trapezoid articulate facet. A stabilizing stem extends outwardly from the inferior surface. The implant further includes a superior surface having a smooth convex shape which articulates with the radius bone An internal surface includes a flat, planar lunate articulate facet and a deep concavity adapted to articulate with the capitate bone. In one embodiment, the stabilizing stem is eliminated and the implant is fixed with a tendon segment or suture. The tendon segment or suture is inserted through a bore in the implant body to fix or inhibit dislocation of the implant.